1. Field of the Invention
The invention relates to a radiation resistant composition for nuclear power plant, in particular, to a cable insulator and/or a sheath material to which an aromatic series oil as a process oil and/or a radiation resistance imparting agent (anti-radiation agent) are/is added with an antioxidant and a radiation resistance is further imparted by a polymer blend.
2. Description of the Related Art
Currently, a cable insulator and/or a sheath material for nuclear facilities such as a nuclear power plant are/is formed of ethylene propylene rubber, polychloroprene rubber and polyethylene, and a method in which a process oil of aromatic series, etc., having a radioprotective effect or an antioxidant is added is generally used in order to impart radiation resistance (anti-radiation).
The aromatic series oil is used as an energy transfer type anti-radiation agent which absorbs radiation energy, and it can be added at a large amount since bleed does not occur. The antioxidant is used in combination of a first antioxidant for trapping/stabilizing a radical generated in a polymer with a second antioxidant which is peroxide decomposing type for decomposing peroxide into alcohol. A decrease in tensile properties and electrical properties, etc., due to radiation degradation can be suppressed by adding the above (e.g., see JP-A 4-268350, JP-A 2-227914 and JP-A 8-96629).
Furthermore, there has been proposed a radiation resistant polymer composition having a radioactive decay polymer added thereto and exhibiting moderate survivability of physical properties after radiation exposure (e.g., see JP-A 2005-48129).
Taking into consideration the case of LOCA (loss-of-coolant accident), nuclear power plants require a composition which withstands a radiation dose of about 760 kGy for a boiling water reactor (BWR) nuclear power plant and of about 2 MGy for a pressurized water reactor (PWR) nuclear power plant.